Taking My Living Room Off The Grid

March 2009

My first major step toward energy independence.

My small solar array has grown over the past year.
Now at 225 Watts on the roof, 400 Watts by the end of the month. I'm running my outdoor
lighting via an inverter. More
details on that project here. By
about 11 AM, my array has replenished all the power used the night before.
The battery bank is at 100%, and the charge controller switches to a float
mode. All the energy that could be collected over the rest of the day
is unused. Time to make my system start paying for itself.

It's a
lot easier to save energy than to create it. First move was to get rid
of the incandescent bulbs, and move to Compact Fluorescent Lighting (CFL).
These take a fraction of the energy to produce the same amount of lumens.
In each of the two lamp fixtures, I'm now using a 20 Watt CFL bulb, which
produces 75 Watts worth of light. I used a Kill-A-Watt meter to verify
each fixture was drawing exactly 20 Watts of grid power.

The next step was to run these lamps from an inverter. I wanted to
verify there was no flicker, hum, or any perceivable different in the
lighting when on grid power, versus running on a Modified Sine Wave (MSW)
inverter. I couldn't detect any difference. I then measured the
DC current to determine the current draw while running from the inverter.
3.40 Amps. 3.4 A x 12 V = 40.8 Watts. The inverter has some
losses as well, but that's pretty close to the expected 40 Watts.

These lights will be run 5 or 6 hours a day typically. 40.8 Watts x
6 hours = 245 Watts. Doable, even with my small array running
the outdoor lighting, security system (CCTV), LinkPro monitor, and the self
consumption power of two charge controllers. With a 70% derating
factored in (typical for solar panels), and my location (5 hours peak sun),
my array collects about 787 Watts. With all my present loads, I
consume 376 Watts per day. Leaving 411 Watts. It's enough for
this project, but I have another 45 Watt solar array waiting to be
installed, and another 130 Watt Kyocera panel on order.

The heart of this project is a $29.99 Vector inverter.
It is a Modified Sine Wave (MSW) type inverter, but the CFL bulbs don't care.

The Test Setup

To verify the quality of the lighting would be the same via a MSW inverter,
I temporarily setup the hardware in the living room. A 400 Watt Vector
inverter with a small 12V battery.

With both lamps up to operating temperature, the total current draw (both
lamps and inverter losses) measured 3.40 Amps.

Two lamps light up our living room reasonable well at night. We have
skylights, so natural lighting keeps the place bright most days. The
inverter and battery are sitting on the floor for the test. An
extension cord is running to the lamp furthest away. Both lamps
operating from the inverter in this picture.

Each lamp is fitted with a 20 Watt GE CFL bulb.

Close-up of the $29 inverter.

Back panel, not much to see.

CFL bulbs are cheap these days.

They are also available in many shapes & sizes. I'm using a pair of
these in an antique desk lamp.

The Installation

The inverter was placed next to the battery bank,
and installed a new outlet in the living room. It operates from the
inverter. The trick was to remotely operate the inverter. If the
inverter is left on all the time, it becomes a parasitic load. This
can be accomplished by using a relay at the inverter and a switch in the
living room. It can also be done with a wireless remote control, which
is the route I've taken.

The 12V wireless kit was purchased at
Amazon for 34.95.
Includes two remotes. Very simple to connect.

The built-in relay in the remote control is limited to 6 Amps. I added
a 30 Amp Bosch type relay to the output so it could supply 12V power to the
inverter when needed.

The wife has some requirements. The installation must be hidden, and
things must operate normally. Not a problem. I selected a
location on the short wall leading to the patio. Marked the location
for the box.

I punched a test hole with a screwdriver. I knew there wouldn't be
much room behind the drywall since this is an exterior wall, with block
construction.

Cleaning up as I go. Yea, I probably should have used a drop cloth.

No way that deep box is going to fit in the wall without busting out the
block behind it. So off to the bandsaw.

Sliced off the bottom of the box, leaving the mounting wings intact.
Note the inverter on the wall in the background.

Done.

The modified box now fits nicely in the opening.

I drilled a hole at the top of the wall to pull the wire through. If I
had good access, I could have drilled down from the attic.

Wouldn't you know it, there's a wall stud right where I drilled. I had
to keyhole the opening to get in the wall space between the drywall and
exterior block wall. I ran a metal fish down the wall. The good
news is I now have an easy way to route the wire into the attic. This
is when the wife starts asking questions. ;-)

The end of the fish was pulled out the opening, and a nylon cord was
attached. After I pulled up the cord, I ran another cord through the
top hole into the attic.

Not the black cable in the foreground, but the white cable in the background
is coming from the living room. Tough to reach without a pole with a
hook on the end of it.

Once I hooked the cord, I pulled it over to me, and tied the 14 gauge power
cord to it. My wife pulled the cord from inside the living room until
the power cord reached the floor.

The end of the cable was then tied to the cord running behind the drywall,
and pulled down to the outlet opening.

The cable was pushed into the keyhole slot I made earlier, and the drywall
is ready for repair.

Me on top of a ladder filling the hole. I'll later sand it, texture it
(spray product), and paint it to match. Wife is straw-bossing, so need
to do a good job!

Since I hacked off the back end of the outlet box, the cable entry slots are
gone. I drilled a hole in the top of the box and fed the cable through
it. Note the wing on the top right of the box. There's another
one on the lower left of the box as well.

When the screws are turned, the wings flip out behind the drywall, clamping
the drywall between the tabs on the top & bottom of the box, and the wings.

Outlet wired up and installed. A little tighter than a regular outlet,
but still plenty of room.

Sorry for the fuzzy pic, but the job is done. Looks like any other
outlet in the room. Same style, same color, same height. I
plugged one lamp in each outlet to prevent something else from being
accidentally plugged in. I will place a discreet decal on the
faceplate (black on clear lettering) indicating this is an alt-power outlet.

Conclusion

The toughest part of this job was having to sneak a power
wire down an exterior wall. I'm sure the pros have specialized tools
for making this a simpler task. But the fact is not even the cable
company does inside the wall installations anymore on existing homes.
They simply bore a hole through the outside of the wall, and run the cables
outside. I could have easily done just that, and ran conduit up the
patio wall. But that wouldn't look as nice, and I'm sure the boss
wouldn't be happy. The results were worth the effort.

When it was all installed, I handed the wife the
remote. She pushed the button, a second later the lights came to life.
It was a bit of work to wire it up, but nothing too technical. As the
she noted, we're going green. My living room lighting is now free.
Nice part is it will work despite what the grid is doing during hurricane
season.

We used the lights all evening as we normally do. Went off
to work in the morning, and by the time I got home, the
LinkPro monitor showed that
the battery bank was 100% once again. The calculations were correct.
The array makes enough juice to run the lights and the other equipment
mentioned earlier.

No more buying batteries for flashlights. Our
lights don't go off when the grid goes down! Now to move onto another
room, and take more lights off the grid.

Update!

The night before last, the lights wouldn't turn on via the remote. Has
been working flawlessly for the past two years. I went into the garage
with the remote, and pushed the button. I heard the relay "click", but
the inverter had no power. A couple more tries, it started working.
Relay contacts were shot. Hey, I only paid a buck for this relay on
Ebay! No problem, I had ten new ones I purchased a few months back.

Nice part about having the hardware on a piece of plywood is easy access,
easy replacement. I swapped one wire at a time. The new relay is
rated for more current, though I didn't exceed the rating of the old one.

A quick press of the remote, it works!

A view of the old relay just before chucking it away. Think I'll avoid
this brand in the future. Probably all made in China, no matter the
brand.